The ISTP is one of the most complex of Jungian character types moving seamlessly from quiet bystander to active participant and leader of the revolution in one fell swoop, then back again to invisible, apparently disinterested introvert. The self-indulgent nature of the ISTP means that they will be full-on, or full off - they don’t do shades of grey! The ISTP is at their best in times of crisis and challenge, but will have little appetite for follow-through. Independent, inscrutable and self-contained the ISTP will be difficult to get to know as they will reveal only what they choose to reveal.

At their best ISTPs are excellent at reacting to problems or crises, needing very little preparation and able to cut to the chase with no preamble or discussion with others, spontaneously grasping the nettle often to the surprise of those who had viewed them as peripheral players. The ISTP doesn’t follow the social mores, nor do they need to engage fully with others and this can give them a distant, aloof persona to others who often don’t quite know where they stand.

Practical, resourceful, adaptable pragmatists, ISTPs possess an excellent capacity for understanding how anything works, displaying logical, detached analysis. They have incredible (often understated), powers of observation and a great talent for logical dispassionate analysis, and getting things to work. Since people rarely conform to laws of physics the ISTP may struggle with interpersonal issues preferring the rationality of scientific experiments to the irrationality of mere mortals with all their foibles, idiosyncrasies and irrationality. They will also be quite private regarding their own personal lives and walk away from conflict, not from fear but as it is just so unproductive! However this means that others may therefore see them as thick-skinned and uncaring.

Practical, pragmatic and realistic the ISTP is self-sufficient and very independent, only really happy when undertaking some risky or interesting activity. Direct to the point of abruptness and tending at times to tread on toes, the ISTP tends to speak literally showing little concern for the impact, and they display coolness under pressure which helps get things fixed but which may not endear them to those around them, (even those for whom they’ve fixed something!)

Ultimately the ISTP wants to be left alone to live their lives and do their jobs the way they see fit, rarely trying to control others and expecting others not to try to control them. But in a crisis, or when the situation needs in-depth understanding, the ISTP will thrive - at least until the crisis is over!

An ISTP will be difficult to know as they will be quiet outsiders looking in until they are ready. One they are clear on what needs to be done, they will, paradoxically, be difficult to budge and will potentially move too quickly without thinking through all the implications.

The ISTP is either full on or apparently full off, and this may confuse those with whom they work. They dislike theories and complexities, preferring facts and data which will help get the job done in the quickest possible time and with the minimum amount of effort. The critical faculty of the ISTP can appear cynical or negative, as they watch from the side-lines.

Others may be taken by surprise by someone who has simply observed and pointed out the down-side who then suddenly becomes animated, energetic and who makes decisions based on logic rather than peoples' feelings. The switch may appear as from someone who is almost exclusively listening to someone who just doesn't listen!

The ISTP has a great ability to analyse facts and store data. This is all internalised, stored in the grey filing cabinets in the brain until called for. Then, when someone argues with the ISTP, the facts, data, empirical evidence, knowledge are brought quickly to bear to quash the arguments.

If an ISTP is not in a position where they can make such full-on contributions, they can sit back and criticise, citing many rational reasons as to why they are right and the existing methods are wrong.

The independent streak in the ISTP means that they will usually display confidence in their own abilities but this means they may also not bring others into the decision-making process. Their desire to get a result in the minimum amount of time also means they may overlook the personal touch, and make them fail to see the 'bigger picture,' and so, by quickly solving a problem, they may create another.

The ISTP is VERY difficult to know and an unusual character type. Like their fellow SPs, ISTPs are fundamentally performers ‘T’s their areas of interest tend to be mechanical and physical rather than artistic like those of ISFPs, and unlike most ESPs they do not present an impression of constant activity. On the contrary, they can lie quite dormant, storing all the data and information in the grey filing cabinets, saving their energy until a project or an adventure they deem worthy of their time arises, and then they launch themselves into this headlong and full throttle.

The apparently hyperactive state that inevitably follows is actually much more controlled than it appears - ISTPs always seem to know what they're doing when it comes to physical or mechanical obstacles but the whole chain of events can present a confusing and paradoxical picture to the outsider, especially those who’ve made up their minds that the ISTP is just a quiet bystander!

ISTPs are equally difficult to understand in their need for personal space, which in turn has an impact on their relationships with others. They need to be able to ‘spread out’ both physically and psychologically which generally implies encroaching to some degree on others’ space, especially if they decide that something or someone else's is going to become their next project. (They are generally quite comfortable, however, with being treated the same way they treat others at least in this respect.)

But because they need such a lot of flexibility to be as spontaneous as they feel they must be, they tend to become as inflexible as the most rigid ‘J’ when someone seems to be threatening their lifestyle (and the response is usually strong and verbose which is yet another stunning contrast to the ‘dormant,’ impassive, detached mode which others may have observed before the backlash).

These territorial considerations are usually critical in relationships with ISTPs. Communication also tends to be a key issue, since they generally express themselves tersely or even non-verbally. When they do actually verbalise, ISTPs are masters of the one-liner, often showing flashes of humour in the most tense situations and this can result in their being seen as thick-skinned or tasteless.

Like most SPs, ISTPs may have trouble with rote and abstract classroom learning, which tend not to be good measures of their actual intelligence. They tend, sometimes with good reason, to be highly sceptical of its practical value. In terms of careers, they are at their best in a crisis, where their natural disregard for rules and authority structures allows them to focus on and tackle the emergency at hand in the most effective way.

As wityh other SPs, ISTPs are energized by responding to their impulses. Sport, both actual and created, appeal to many ISTPs for the sheer sensory experience. They work in short bursts of incredible energy with a no-nonsense realism. The uncanny troubleshooting ability which predisposes many ISTPs to hands-on diagnostics (especially with machinery and computers) or detective work stems from this combination.

In a team situation the ISTP will use their love and store of knowledge to bring a clear explanation of how and why things happen, using empirical data and evidence, hypotheses and rational thinking. The ISTP may not be the most vocal, but when the discussions enter the arena which holds their interest, they will become quite outspoken and very clear thinking.